Varying pH influences the motility of Helicobacter pylori more strongly in porcine gastric mucin solutions than in broth.

<emph type="bold-italic">Helicobacter pylori</emph>, a pathogen which inhabit the gastric mucus has to swim across the naturally occurring pH gradient in the mucus layer varying from 2-4 in the lumen to 7 on the epithelial surface. The mucus has a pH-dependent viscoelasticity forming a gel at low pH, whereas at higher pH it is solution-like. Previous studies have shown that <emph type="bold-italic">H. pylori were immobile in porcine gastric mucin (PGM) below pH 4. How much of this effect is due to gelation of PGM and how much due to the effects of pH on the flagellar motors is unclear. To address this question we compared the translation and rotational motion of the bacteria in PGM versus broth at different pH. In broth,</emph> H. pylori swimming speed increased as pH was lowered from pH 7 to 4, followed by a drop in speed below pH4 indicating decrease of proton motive force, whereas in PGM the speed peaked at pH 5 and bacteria became immobile below pH3, indicating the increase in viscosity in PGM dominating the loss of motility. The body rotation rate is weakly dependent on pH in broth. in PGM the bacteria stuck in the low pH gel rotate much faster than the mobile bacteria at higher pH's, indicating that bacteria can sense the environment's mechanical properties and attempt to free themselves from being immobilized.

Funded by NSF PHY1410798 .